The built in font are embedded into the firmware. I know that on the 505 you can change the default font but that involves modding the firmware and reflashing it.
Epub file will take CSS codes that can specify fonts. For example I have Caecilia font in a folder called 'fonts' I created and when I convert my ebooks in calibre I use the code:
Code:
@font-face {
font-family: 'Caecilia', serif, sans-serif;
font-style: normal;
font-weight: normal;
src:url(res:///Data/fonts/CaeciliaLTStd-Roman.otf)
}
@font-face {
font-style: italic;
font-family: 'Caecilia', serif, sans-serif;
font-weight: normal;
src:url(res:///Data/fonts/CaeciliaLTStd-Italic.otf)
}
@font-face {
font-style: italic;
font-family: 'Caecilia', serif, sans-serif;
font-weight: bold;
src:url(res:///Data/fonts/CaeciliaLTStd-BoldItalic.otf)
}
@font-face {
font-style: normal;
font-family: 'Caecilia', serif, sans-serif;
font-weight: bold;
src:url(res:///Data/fonts/CaeciliaLTStd-Bold.otf)
}
body {
font-family: "Caecilia", serif;
}